Broadly speaking, heat engine driven heat pump systems are well known and have been refined for internal space conditioning use as shown in U.S. Pat. No. 4,991,450. Because heat engines, such as natural gas driven internal combustion engines, provide excess and otherwise unused heat in the motive process subsystems have been developed which recapture otherwise waste heat which is circulating in the engine coolant. U.S. Pat. Nos. 5,003,788, 5,020,320, 5,029,449, 5,099,651 and are further examples of this type of subsystem.
Further improvements in these subsystems provide advantages in waste heat recovery to the application of such heat to the occupants of the space and in some instances for other purposes.
Traditionally heat pumps such as electric motor driven heat pumps do not have sufficient excess available heat for use in such subsystems.
Further refinements and improvements in waste heat recovery subsystems are important since they increase the overall coefficient of performance (COP) of the heat pump system as well as providing overall operational economies by reducing the amount of externally supplied auxiliary heat and increase the comfort of the delivered air. In some systems the extra heat is used for domestic water heating and other purposes. Thus, the user obtains these benefits as an "extra" from the recovery of the waste heat.
While this invention is described herein in association with a gas fueled internal combustion engine, broader applications to other "heat" engines, such as turbines, may be possible. The coolant fluid employed in the subsystem may be one of various conventional types, such as ethylene glycol-water or propylene glycol-water mixtures.